CVE-2018-19986: Improper Neutralization of Special Elements used in an OS Command

In the /HNAP1/SetRouterSettings message, the RemotePort parameter is vulnerable, and the vulnerability affects D-Link DIR-818LW Rev.A 2.05.B03 and DIR-822 B1 202KRb06 devices. In the SetRouterSettings.php source code, the RemotePort parameter is saved in the $path_inf_wan1."/web" internal configuration memory without any regex checking. And in the IPTWAN_build_command function of the iptwan.php source code, the data in $path_inf_wan1."/web" is used with the iptables command without any regex checking. A vulnerable /HNAP1/SetRouterSettings XML message could have shell metacharacters in the RemotePort element such as the `telnetd` string.